Field of the Invention
The invention relates to a method for the common transmission of digital source and control data between data sources and sinks being connected through data lines, in which source and control data are transmitted in a format prescribing a clocked sequence of individual bit groups of equal length.
The present invention shows a network with ring-like architecture, in which subscribers forming data sources and data sinks are connected through a single data line. Through that data line, the source and control data are transferred in a continuous data stream which is synchronous to a clock signal. The clock signal is generated by a single subscriber. All other subscribers synchronize themselves to the clock signal. Purely asynchronous data transmission methods have to be differentiated therefrom as packet or package-oriented data transmission methods, for example ATM-methods.
Such methods are used wherever different electrical and electronic devices that are intended to exchange information with one another are linked to one another through the use of data lines in what is sometimes a complicated way. In the audio field, for instance, communication between interlinked data sources on one hand, such as CD players, radio receivers and cassette tape recorders, and the data sinks connected with them on the other hand, such as amplifier-speaker combinations, can be controlled by such a method.
In the course of development of CD players, the so-called SPDIF format (Sony/Philips Digital Interface Format), which is also known by the designation IEC 958, has become established as the standard. That format prescribes transmission of the data in a frame that includes two subframes or bit groups. Each subframe includes a preamble of four bits for control data, followed by 24 bits for source data and ending with four bits for special control data. One subframe of each frame is assigned to the left audio channel, and the other subframe is assigned to the right audio channel.
Since the rigid structure of that format has proved to be disadvantageous for data transmission in complex communications systems, co-pending U.S. application Ser. No. 08/595,838 now U.S. Pat. No. 5,844,953) entitled "Method for Common Transmission of Digital Source and Control Data Between Data Sources and Data Sinks Connected through Data Lines" has been filed simultaneously with the instant application, in which a substantially more-flexible format for data transmission is described.
Fundamentally, all of those methods have in common the fact that both source and control data must be converted into a fixedly specified format prior to transmission. On one hand, that can be time-consuming and can cause unacceptable delays in time-critical applications. On the other hand, with a specified transmission format, only control data that are defined for transmission with that format, or in other words that are contained in the "instruction set" of the particular transmission format, which set includes the individual control data, can be transmitted. Moreover, the length of the data words that can be transmitted is restricted by the length of the individual bit groups.